One form of seat having an adjustable seat portion and a backrest portion which is adapted to be adjusted in respect to its angle of inclination, for example an office chair, comprises a seat carrier assembly on which is carried a seat portion which is adjustable in regard to its angle of inclination, together with a backrest portion which is also adjustable in its angle of inclination. The seat comprises a first gas spring unit which is connected to the backrest portion for adjusting the inclination thereof and at least one further gas spring unit which is operatively connected to the seat portion for adjusting the inclination of the seat portion. An actuating lever is operatively connected to the valve actuating pins of the gas spring units, by way of a suitable connecting system, and the actuating lever is pivotable about a pivot point in a first direction and also in a second direction which is perpendicular thereto, for producing the respective adjustment movements. Such a seat is to be found for example in EU patent application No. 0 022 933.
In that seat, pivotal movement of the actuating lever in the first direction makes it possible to adjust the angle of inclination of the seat portion of the seat or, by returning the lever by way of the starting position thereof, the angle of inclination of the backrest portion. Pivoting the actuating lever in the second direction provides for joint pivotal movement of the seat portion and the backrest portion to adjust the angles of inclination thereof in combination. Therefore, that seat construction makes it possible to pivot either only the seat portion or only the backrest portion, as desired, or it can provide that the seat portion and the backrest portion can only be jointly pivoted for adjustment as a unit.